Nitrogen Fertilization and Cutting Frequency, Yield and Chemical Composition of Five Tropical Grasses

Abstract

Five tropical forage grasses: Star (Cynodon nlemfuensis), Transvala digit (Digitaria decumbens), Pangola (Digitaria decumbens) and two Limpos (Hemarthria altissima, Bigalta and Greenalta), were cultivated without irrigation for 1.5 years at the Corozal Agricultural Experiment Substation to study the effects of 3 N fertilization levels and 3 harvest intervals (30, 45, and 60 days) on the green forage (GF), dry forage (DF), and crude protein (CP) yields and on the dry matter (DM), CP, P, and K contents. The soil is a Corozal clay (Uitisol). N levels, as (NH₄)₂SO₄, applied after each harvest, included low, 224; medium, 448; and high, 896 kg/ha/yr. P and K were applied at rates of 112 and 336 kg/ha/yr, respectively. DM content and DF and CP yields increased significantly with longer harvest intervals. The medium N level resulted in the highest CP yields, except in the case of Star grass, in which high N fertilization gave greater CP yield. Bigalta, Star, and Transvala digit cultivars exhibited the highest GF, DF, and CP yields. DF yields (means across the 3 harvest intervals and the 3 N levels) for Bigalta, Greenalta, Transvala, Star, and Pangola grasses were 35,421; 29,209; 31 ,699; 32,383; and 24,461 kg/ha/yr, respectively.